When a general active region of a DRAM is formed, the area of the center portion of the active region, that serves as a bit line contact region, is increased in order to increase a current amount and reduce a contact resistance with a bit line. The active region having an increased center portion is called a G-type active region.
FIG. 1 is a layout of an exposure mask for I-type active region. An exposure mask 100 includes a bar shaped light-blocking pattern 110 to define an I-type active region.
FIGS. 2a and 2b are top-views illustrating a double patterning process of forming an I-type active region of a semiconductor device. A first hard mask layer 214 is formed over a semiconductor substrate 200. A lithography process is performed using exposure mask 100 of FIG. 1 to form a second hard mask pattern 220. An exposing process is performed using exposure mask 100 of FIG. 1 to form a photoresist pattern 225 which is disposed between second hard mask patterns 220. First hard mask layer 214 is etched using second hard mask pattern 220 and photoresist pattern 225 as a mask to form a first hard mask pattern 230 that defines an I-type active region.
In order to form a hard mask pattern defining a G-type active region, an optical proximity correction (“OPC”) process is performed so that a given thickness of the center portion of light-blocking pattern 110 of FIG. 1 is protruded toward both sides in a minor axis direction of the G-type active region. In the OPC process, a margin for protruding the center portion is insufficient to increase a bit line contact resistance and reduce the current amount, thereby degrading characteristics of the device.